SummaryIt was shown in this study that patients with one second values greater than 50 % have definitely less positive electrocardiographic criteria (as defined for the purpose of the study) than these with one second values greater than 50°%. A QRS axis greater than 90°in the frontal plane and a clockwise rotation in the horizontal plane were most frequently found. These two criteria, however, were never found in patients with one second value greater than 50 %. The latter was also true for a P greater than 1.5 mm in the right precordial leads. Microvoltage and a P greater than 2 mm in the standard leads were, however, rather frequently present in cases with a one second value higher than 50 %. Finally, it should he emphasized that in some patients with a very low one second value the electrocardiogram was essentially normal.